tridactyle

Now when the latter arise from the summit of a spine they form in fact a rude tridactyle pedicellaria, and such may be seen on the same spine together with the three lower branches.

VII. Miscellaneous Objections to the Theory of Natural Selection 1909

This may be inferred from their manner of development in the individual, as well as from a long and perfect series of gradations in different species and genera, from simple granules to ordinary spines, to perfect tridactyle pedicellariæ.

VII. Miscellaneous Objections to the Theory of Natural Selection 1909

There is no more difficulty in understanding how the branched spines of some ancient echinoderm, which served as a defence, became developed through natural selection into tridactyle pedicellariæ, than in understanding the development of the pincers of crustaceans, through slight, serviceable modifications in the ultimate and penultimate segments of a limb, which was at first used solely for locomotion.

VII. Miscellaneous Objections to the Theory of Natural Selection 1909

” Paradoxical as this may appear to Mr. Mivart, tridactyle forcepses, immovably fixed at the base, but capable of a snapping action, certainly exist on some starfishes; and this is intelligible if they serve, at least in part, as a means of defence.

VII. Miscellaneous Objections to the Theory of Natural Selection 1909

But, as far as structure is concerned, I can see no similarity between tridactyle pedicellariae and avicularia.

VII. Miscellaneous Objections to the Theory of Natural Selection 1909

The Echinodermata (star-fishes, sea-urchins, &c.) are furnished with remarkable organs, called pedicellariæ, which consist, when well developed, of a tridactyle forceps—that is, of one formed of three serrated arms, neatly fitting together and placed on the summit of a flexible stem, moved by muscles.

VII. Miscellaneous Objections to the Theory of Natural Selection 1909

There are tridactyle footprints in the red sandstones of

The Testimony of the Rocks or, Geology in Its Bearings on the Two Theologies, Natural and Revealed Hugh Miller 1829